Habitat Suitability Index
Habitat Suitability Index
Evaluates (pond) habitat quality
10 suitability indices, all of which are factors known to
affect great crested newts
Combined index, between 0 and 1
– 0 indicates unsuitable habitat
– 1 optimal habitat
Ponds with higher index more likely to support great
crested newts
Data collection & calculation of HSI
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10 factors are scored for the pond
Convert to SI scores ranging from 0.01- 1
(Do not give any SI score a value of 0)
The 10 scores are then multiplied together
The tenth root of this number is then calculated
The calculated habitat suitability index should be
between 1 and close to 0
• H S I = (SI1 x SI2 x SI3 x SI4 x SI5 x SI6 x SI7x
SI8 x SI9 x SI10) ^(1/10)
Categorisation of HSI scores
HSI
Pond suitability
<0.5
Poor
0.5- 0.59
Below average
0.6- 0.69
Average
0.7- 0.79
Good
>0.8
Excellent
Geographic Location (SI-1)
Geographic location (SI-1)
Pond Area (SI-2)
Pond Permanence (SI-3)
Water Quality (SI-4)
Water catchment/source
Plenty of inverts
Submerged vegetation
Don’t confuse water clarity with
quality
Water Quality
Category
SI
Criteria
Good
1.0
Abundant & diverse communities
Netting = diverse inverts including
mayfly larvae & water shrimps
Moderate
0.67
Moderate invert diversity
Poor
0.33
Low invert diversity (e.g.species
such as midge and mosquito
larvae), few submerged plants
Bad
0.01
Clearly polluted, only pollution
tolerant species (rat-tailed
maggots), no submerged plants
Shading (SI-5)
• Estimate the % of
perimeter shaded (usually
by trees)
• Include trees that cast a
shade to at least 1m from
shore
• Does not include emergent
vegetation
• Make estimate in May- end
of Sept
Shading (SI-5)
Heavily shaded ponds less
likely to support great
crested newt
Waterfowl (SI-6)
Impacts waterfowl have on ponds and newts:
• Remove aquatic vegetation
• Pollute water
• Stir up sediments
• Some waterfowl actively hunt adult newts and
larvae
Fish (SI 7)
Fish (SI 7)
Category
SI
Criteria
Absent
1
Absent
Possible
0.67
Possible
Minor
0.33
Minor (Crucian Carp &
sticklebacks)
Major
0.01
Major (other species or
carp/sticklebacks in dense
populations)
Pond Count (density) (SI-8)
Higher pond densities – more
likely to support great crested
newt
Terrestrial Habitat (SI-9)
• Good terrestrial habitat offers- cover, foraging
opportunities
• Habitat includes meadow, rough grassland, hedges,
scrub, woodland and gardens
Category
SI
Criteria
Good
1
Extensive area of habitat
offering good areas for foraging
and shelter.
> 75% of available area
Moderate
0.67
Habitat offers opportunities for
foraging and shelter.
25-75% of available area
Poor
0.33
Habitat offers little opportunity
for foraging and shelter
< 25% of area
None
0.01
No suitable habitat around the
pond
Macrophyte cover (plants) (SI–10)
Specific pond types - water tanks
© Ben Driver
Specific pond types – garden ponds
© Ben Driver
Flooded excavations
The largest newt populations are found in disused
mineral sites (also clay and chalk pits)
References
• Oldham, R.S., Keeble, J., Swan M.J.S & Jeffcote
M. (2000). Evaluating the suitability of habitat for
the Great Crested Newt (Triturus cristatus).
Herpetological Journal 10 (4), 143-155
Photographs
• Copyright of all photographs remains with the photographers and
ARC.
• These photographs should not be used for purposes other than
NARRS training without the permission of the photographers.